LONDON, Feb. 4 -- Two British High Court judges ruled against releasing documents describing the treatment of a British detainee at the Guantanamo Bay prison, but made clear their reluctance, saying that the United States had threatened to withhold intelligence cooperation with Britain if the information were made public.

"We did not consider that a democracy governed by the rule of law would expect a court in another democracy to suppress a summary of the evidence . . . relevant to allegations of torture and cruel, inhumane, or degrading treatment, politically embarrassing though it might be," Justice John Thomas and Justice David Lloyd Jones wrote.

The judges decided not to release information, supplied to the court by U.S. officials, concerning the treatment of Binyam Mohamed, 31, an Ethiopian-born British resident who was arrested in Pakistan in 2002.

The decision touched off a wave of anger at Washington from the floor of Parliament to the offices of human rights groups.

"The government is going to have to do some pretty careful explaining about what's going on," said David Davis, a top Conservative Party leader, speaking in the House of Commons.

Davis said it appeared the U.S. government had "threatened" the British government about the repercussions if details of the case were made public. "Frankly, it is none of their business what our courts do," he said.

"The ruling implies that torture has taken place in the Mohamed case, that British agencies may have been complicit, and further, that the United States government has threatened our High Court that if it releases this information the U.S. government will withdraw its intelligence cooperation with the United Kingdom," Davis said.

Mohamed was initially charged with planning a "dirty bomb" attack in the United States. Those charges were later dropped, but Mohamed has been held at the Guantanamo detention center in Cuba since September 2004 after allegedly confessing to being an al-Qaeda operative.

Mohamed says that evidence against him is based on confessions obtained by torture at the hands of U.S. officials and allies in "secret prisons" in Morocco and Afghanistan and later in Guantanamo.

Wednesday's ruling was part of a long-running legal battle by Mohamed's attorneys, who argue that he has committed no crime and is a victim of torture and rendition by U.S. officials, with British cooperation.

Attorneys for several British and American news media organizations petitioned the court to release the information it had about Mohamed's treatment, which had been redacted from a court ruling last summer.

On Wednesday, the judges turned down the request to release the documents, saying that the United States continued to threaten to punish Britain by withholding intelligence cooperation if the court released details of Mohamed's treatment.

Clive Stafford Smith, Mohamed's attorney, told reporters that by not disclosing the evidence, Britain was guilty of "capitulation to blackmail."

"It is hardly Britain's finest hour," he said. "As the judges say, it is up to President Obama to put his money where his mouth is. He must repudiate his predecessor's reprehensible policy."

Officials in Prime Minister Gordon Brown's office said they are unaware of any threat from the Obama administration to withhold cooperation. "We have not engaged with the new administration on the detail of this case," a Brown spokesman told reporters.

Also Wednesday, the American Civil Liberties Union sent a letter to Secretary of State Hillary Rodham Clinton, urging her to clarify the Obama administration's position on the Mohamed case and to reject what it described as the Bush administration's policy of using false claims of national security to avoid judicial review of controversial programs.

Anthony D. Romero, head of the ACLU, said, "The latest revelation is completely at odds with President Obama's executive orders that ban torture and end rendition, as well as his promise to restore the rule of law."